Tumor development typically progresses through several stages:
1. Initiation: This is the first step where normal cells undergo genetic mutations due to factors like carcinogens, radiation, or inherited genetic defects. 2. Promotion: Mutated cells begin to multiply abnormally, but the growth is still reversible at this stage. 3. Progression: The tumor becomes malignant as cells acquire more mutations, leading to increased growth rate, invasion of nearby tissues, and the potential to metastasize.